1. Field of the Invention
The present invention relates to an ejector cycle, more particularly, to an ejector insulation structure for improving cooling capacity and coefficient of performance (COP) in the ejector cycle.
2. Description of the Related Art
FIG. 5 is a schematic diagram showing an ejector cycle in a prior art, and FIG. 6 is a Mollier diagram showing operational states of the ejector cycle in FIG. 5. Refrigerant conditions designated by R1 to R9 in the ejector cycle in FIG. 5 correspond to the operation points on the Mollier diagram in FIG. 6 indicated by the same reference numerals.
In this ejector cycle, high-temperature high-pressure refrigerant discharged from a compressor 1 is cooled and condensed in a condenser 2. High-pressure refrigerant from the condenser 2 is decompressed in a nozzle of an ejector 4 and is mixed with gas refrigerant sucked from an evaporator 3. Refrigerant flowing out of an outlet of the ejector 4 is introduced into a gas-liquid separator 5 to be separated into gas refrigerant and liquid refrigerant. Gas refrigerant from the gas-liquid separator 5 is introduced to the compressor 1 and liquid refrigerant from the gas-liquid separator 5 is introduced to the evaporator 3 to be evaporated in the evaporator 3.
In the ejector cycle, the liquid refrigerant, supplied with a driving flow driven by the compressor 1, evaporates in the evaporator 3 to produce a cooling capacity Q. The amount of energy supplied from the compressor 1 can be indicated by the product of an amount of a driving flow Gn and an enthalpy difference Δin. Here, the enthalpy difference Δin is a difference between a saturated gas enthalpy at the pressure of the outlet of the evaporator 3, and a refrigerant enthalpy at an outlet of the nozzle.
In contrast, heat loss in the ejector 4 is caused by a heat exchange with an external side. That is, a heat loss Δi1 is generated in a mixing portion and a diffuser of the ejector 4, in which kinetic energy of refrigerant is transformed to pressure energy of the refrigerant. When the heat loss Δi1 is increased, the refrigerant enthalpy at the inlet portion of the evaporator 3 increases because not only the liquid refrigerant but the gas refrigerant is supplied from the gas-liquid separator 5 to the evaporator 3. In this case, an energy loss Δi2 is caused in the evaporator 3.
Consequently, an actual cooling capacity Q is calculated by the following formula (1)Q=Gn×(Δin −Δi1 −Δi2)  (1)
In a case where the ejector 4 is provided in a forced convection flow, it is important to suppress the heat losses Δi1 and Δi2 caused due to the heat exchange in the ejector 4 with the external side.